Analog Devices Inc./Maxim Integrated MAX6721UTLTD3

Overview

MAX6721UTLTD3 from Maxim Integrated is a dual-voltage microprocessor supervisory IC that monitors VCC1 (primary supply) and VCC2 (secondary supply), asserts active-low reset when either falls below factory-trimmed thresholds (VTH1 = 4.625V, VTH2 = 3.075V), maintains reset for 210ms minimum timeout, and includes watchdog timer with 35s startup/1.12s normal mode. It operates over –40°C to +125°C in industrial power management systems.

For engineers reviewing the MAX6721UTLTD3 datasheet, MAX6721UTLTD3 pinout, MAX6721UTLTD3 application, or MAX6721UTLTD3 equivalent, key selection criteria include guaranteed reset validity down to VCC1/VCC2 = 0.8V, 14µA typical supply current at 3.6V, push-pull RST output referenced to VCC1, and integrated watchdog disable capability via unconnected WDI.

Technical Context

The MAX6721UTLTD3 implements dual independent voltage monitoring with factory-trimmed thresholds-VTH1 = 4.625V (±125mV) on VCC1 and VTH2 = 3.075V (±75mV) on VCC2-and guarantees correct reset logic state as long as either supply remains ≥0.8V. Its watchdog timer features two-phase operation: 35s minimum startup period after any reset event, followed by 1.12s minimum normal timeout upon first valid WDI edge.

Reset assertion is triggered by VCC1/VCC2 undervoltage, manual-reset input (MR) low, or watchdog timeout; reset deassertion requires all monitored voltages to exceed thresholds plus full 210ms timeout. The device uses internal 626.5mV reference for RSTIN/PFI inputs and provides push-pull RST output with VOH ≥0.8×VCC1 at ISOURCE = 800µA.

Key Specifications

Pinout & Package

MAX6721UTLTD3 is housed in a 6-pin SOT23 package with 1.6mm × 2.9mm footprint and 0.95mm height, compatible with standard reflow profiles and space-constrained PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-voltage supervisory applications.

Compared with TPS3808G33DBVR and ADM6712S33ARTZ-RL, MAX6721UTLTD3 uniquely integrates dual independent voltage monitoring, programmable watchdog timing, and manual reset in a single 6-pin SOT23-reducing component count, PCB area, and qualification effort for complex embedded systems requiring multi-rail reliability.

Availability

MAX6721UTLTD3 is available at Aetrix Electronics and suitable for industrial PLC power monitoring, automotive ADAS camera modules, and network router line cards requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6721UTLTD3 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power management ICs for demanding industrial, automotive, and communications applications.

The MAX6715A–MAX6729A family delivers ultra-low-voltage microprocessor supervisory circuits optimized for dual/triple supply monitoring in space-constrained, high-reliability systems operating from –40°C to +125°C.

FAQ

What is the exact reset timeout period for MAX6721UTLTD3?

The MAX6721UTLTD3 has a guaranteed minimum reset timeout period of 210ms after all monitored supplies rise above their thresholds. This value is fixed by the "D3" suffix in the part number and is characterized over the full –40°C to +125°C temperature range. Typical timeout is 210ms, with maximum specified at 280ms under worst-case conditions.

Does MAX6721UTLTD3 support monitoring a third voltage rail?

No, MAX6721UTLTD3 does not support third-rail monitoring. It is a dual-supply supervisor with dedicated VCC1 and VCC2 inputs. For triple-voltage supervision, consider MAX6723UTLTD3 or MAX6725UTLTD3, which include the RSTIN pin for externally adjustable threshold monitoring down to 0.626V.

How is the watchdog timer disabled on MAX6721UTLTD3?

The watchdog timer on MAX6721UTLTD3 is disabled by leaving the WDI pin unconnected. An internal 200nA current source detects the open state and inhibits watchdog functionality. Do not connect WDI to any node sourcing more than 50nA, as this may falsely enable the watchdog or cause erratic behavior.

What is the function of the MR pin on MAX6721UTLTD3?

The MR (manual-reset) pin on MAX6721UTLTD3 is an active-low input with internal 50kΩ pullup to VCC1. Pulling MR low forces immediate reset assertion, which remains active for the full 210ms timeout period after MR returns high. It enables hardware-initiated resets for field service, test modes, or emergency shutdown without software involvement.

Can MAX6721UTLTD3 operate with VCC1 = 3.3V and VCC2 = 1.8V?

Yes, MAX6721UTLTD3 supports VCC1 = 3.3V and VCC2 = 1.8V. Its VCC1 threshold is fixed at 4.625V, so it will assert reset if VCC1 drops below that level-making it unsuitable for direct 3.3V primary rail monitoring. However, it can supervise a 3.3V VCC2 rail (threshold 3.075V) while VCC1 powers the IC from a higher rail (e.g., 5V). For 3.3V-primary applications, select MAX6720UTLTD3 (VTH1 = 3.075V).